UPDATE: I have spent about 5M more credits since this post and have updated results - click here to see them! Ok, I promised to do a little experiment to.
From personal experience, I believe a Regular Spectre Pack wins, hands down! The only time you should even think about buying a Premium Spectre Pack (PSP) is if you've just.
I'm frankly surprised that we managed to exceed the lofty goals of Operation Olympus this weekend, especially given the fact that I only had time to contribute a few matches.
As most ME3 Online Multiplayer fans know, this weekend 10-12 August is another N7 Operation. It actually starts in 20 minutes, perfect timing to post this then start playing! Here.